MC1102790 - Microsoft Teams: New file attachment feature in external 1:1 and group chats

We're introducing a new capability in Microsoft Teams that allows users to attach files when chatting with external users in 1:1 and group chats. This enhancement improves collaboration by enabling seamless file sharing across organizational boundaries.

This message applies to Teams for Windows desktop, Teams for Mac desktop, and Teams for the web.

This message is associated with Microsoft 365 Roadmap ID 492625.

When this will happen:

Targeted Release: We will begin rolling out early July 2025 and expect to complete by mid-July 2025.

General Availability (Worldwide): We will begin rolling out mid-July 2025 and expect to complete by late July 2025.

How this will affect your organization:

Before this rollout, users had no option to attach file to compose box in chats with external users. The workaround was to copy and paste the link to a file into the chat compose box.

After this rollout, when enabled by admins, users will see an Attach file option in the + menu of the chat compose box when messaging external users. This allows them to include files in their messages, enhancing collaboration with external partners:

Any file shared by an external user will have an External tag:

This feature is off by default and requires admin configuration.

What you need to do to prepare:

Admins can enable this feature by setting the FileSharingInChatsWithExternalUsers policy to true using PowerShell.

For configuration guidance, refer to Set-CsTeamsFilesPolicy (MicrosoftTeamsPowerShell) | Microsoft Learn (will be updated before rollout).